| |
| Export cpu topology info via sysfs. Items (attributes) are similar |
| to /proc/cpuinfo. |
| |
| 1) /sys/devices/system/cpu/cpuX/topology/physical_package_id: |
| represent the physical package id of cpu X; |
| 2) /sys/devices/system/cpu/cpuX/topology/core_id: |
| represent the cpu core id to cpu X; |
| 3) /sys/devices/system/cpu/cpuX/topology/thread_siblings: |
| represent the thread siblings to cpu X in the same core; |
| 4) /sys/devices/system/cpu/cpuX/topology/core_siblings: |
| represent the thread siblings to cpu X in the same physical package; |
| |
| To implement it in an architecture-neutral way, a new source file, |
| drivers/base/topology.c, is to export the 4 attributes. |
| |
| If one architecture wants to support this feature, it just needs to |
| implement 4 defines, typically in file include/asm-XXX/topology.h. |
| The 4 defines are: |
| #define topology_physical_package_id(cpu) |
| #define topology_core_id(cpu) |
| #define topology_thread_siblings(cpu) |
| #define topology_core_siblings(cpu) |
| |
| The type of **_id is int. |
| The type of siblings is cpumask_t. |
| |
| To be consistent on all architectures, the 4 attributes should have |
| deafult values if their values are unavailable. Below is the rule. |
| 1) physical_package_id: If cpu has no physical package id, -1 is the |
| default value. |
| 2) core_id: If cpu doesn't support multi-core, its core id is 0. |
| 3) thread_siblings: Just include itself, if the cpu doesn't support |
| HT/multi-thread. |
| 4) core_siblings: Just include itself, if the cpu doesn't support |
| multi-core and HT/Multi-thread. |
| |
| So be careful when declaring the 4 defines in include/asm-XXX/topology.h. |
| |
| If an attribute isn't defined on an architecture, it won't be exported. |
| |
